Significance of the parkin gene and protein in understanding Parkinson's disease

Parkinsonism in Genetic Neurodevelopmental Disorders: A Systematic Review

Background

With advances in clinical genetic testing, associations between genetic neurodevelopmental disorders and parkinsonism are increasingly recognized. In this review, we aimed to provide a comprehensive overview of reports on parkinsonism in genetic neurodevelopmental disorders and summarize findings related to genetic diagnosis, clinical features and proposed disease mechanisms.

Methods

A systematic literature review was conducted in PubMed and Embase on June 15, 2021. Search terms for parkinsonism and genetic neurodevelopmental disorders, using generic terms and the Human Phenotype Ontology, were combined. Study characteristics and descriptive data were extracted from the articles using a modified version of the Cochrane Consumers and Communication Review Group's data extraction template. The protocol was registered in PROSPERO (CRD42020191035).

Results

The literature search yielded 208 reports for data-extraction, describing 69 genetic disorders in 422 patients. The five most reported from most to least frequent were: 22q11.2 deletion syndrome, beta-propeller protein-associated neurodegeneration, Down syndrome, cerebrotendinous xanthomatosis, and Rett syndrome. Notable findings were an almost equal male to female ratio, an early median age of motor onset (26 years old) and rigidity being more common than rest tremor. Results of dopaminergic imaging and response to antiparkinsonian medication often supported the neurodegenerative nature of parkinsonism. Moreover, neuropathology results showed neuronal loss in the majority of cases. Proposed disease mechanisms included aberrant mitochondrial function and disruptions in neurotransmitter metabolism, endosomal trafficking, and the autophagic-lysosomal and ubiquitin-proteasome system.

Conclusion

Parkinsonism has been reported in many GNDs. Findings from this study may provide clues for further research and improve management of patients with GNDs and/or parkinsonism.

Improved pharmacological properties of nitrotyrosine drug via fluorination: A theoretical study

It has become obvious that fluorinated drugs have a significant role in medicinal applications. In this study, the fluorination of 3-nitrotyrosine as an anti-Parkinson and anti-Alzheimer drug was explored using density functional theory calculations. We have investigated the most important chemical properties of 3-nitrotyrosine that affect the pharmacological activity of the drug. We found that the intramolecular hydrogen bonding and intramolecular charge of the drug were influenced by fluorine substitution. Our results also reveal that the fluorination altered the stability, solubility, and molecular polarity of the 3-nitrotyrosine drug. The density of state analysis also determines sharp resonance states of fluorine atoms with the 3-nitrotyrosine drug states particularly in the highest molecular orbital reigns, suggesting hybridization of the fluorine states with the state of the drug. Moreover, our results show that the electronic spectra of fluorinated derivatives of 3-nitrotyrosine drug exhibit a red shift toward higher wavelengths (lower energies). Our calculations show that the free energy transfers of fluorinated derivatives of the 3-nitrotyrosine drug in water were negative that it meant that the designed molecules dissolving in aqueous phase occurred simultaneously. Consequently, the results of the present study show that the fluorination of 3-nitrotyrosine drug could be considered as a promising strategy to design useful drugs with better pharmacological properties.

Autophagy in light-induced retinal damage

Vision is reliant upon converting photon signals to electrical information which is interpreted by the brain and therefore allowing us to receive information about our surroundings. However, when exposed to excessive light, photoreceptors and other types of cells in the retina can undergo light-induced cell death, termed light-induced retinal damage. In this review, we summarize our current knowledge regarding molecular events in the retina after excessive light exposure and mechanisms of light-induced retinal damage. We also introduce works which investigate potential roles of autophagy, an essential cellular mechanism required for maintaining homeostasis under stress conditions, in the illuminated retina and animal models of light-induced retinal damage.

CD 4+ T cells in the pathobiology of neurodegenerative disorders

CD4+ T cells orchestrate innate and adaptive immunity. In the central nervous system they modulate immune responses including cell trafficking and glial neuroregulatory functions through an array of soluble molecules cell-cell interactions affecting tissue homeostasis. During disease their roles evolve to an auto-aggressive or, alternatively, protective phenotype. How such a balance is struck in the setting of neurodegenerative disorders may reflect a dichotomy between regulatory T cell, anti-inflammatory and neuroprotective activities versus effector T cell inflammation and neurodegeneration. Interestingly, such roles may show commonalities amongst neurodegenerative diseases. Herein we focus on strategies to modulate such CD4+ T cell responses for therapeutic gain.

Syndromic approach to Parkinson's disease: role of functional imaging

Current evidence from monogenic Parkinson's disease (PD) supports the view that PD is a clinical syndrome, rather than a single disease entity, and that the heterogeneity of PD indeed reflects different pathogenesis. Recent developments in functional imaging have enabled the in vivo assessment of cellular and molecular pathology of PD with respect to temporal and topographical patterns. We propose that this new technology will be useful for linking monogenic and sporadic PD, and thus, for classifying PD based on the pathogenesis. It will be also useful in clinico-genetic studies exploring susceptibility factors and at-risk groups, which are important for neuroprotective treatment when it becomes available.

Epidemiological, clinical, and genetic characteristics of early-onset parkinsonism

In this review we discuss the epidemiological, clinical, and genetic characteristics of early-onset parkinsonism, defined as parkinsonism starting before age 40 (sometimes 50) years. Juvenile parkinsonism is very rare and is the result of various secondary or genetic causes. In patients with onset at or above age 21 years, secondary causes require exclusion but are rare; most cases with a fairly pure parkinsonian syndrome (eg, young-onset Parkinson's disease; YOPD) are due to typical Lewy-body Parkinson's disease or, less commonly, genetic causes. In comparison with patients with late-onset disease, most patients with YOPD progress more slowly in terms of motor features and have a longer disease course with preservation of cognitive function, but typically develop motor fluctuations and dyskinesias earlier. Patients with YOPD generally experience a greater effect in their lives than those with late onset, with poorer social adjustment, higher rates of depression, and lower quality of life. Management of YOPD must therefore aim to maintain occupational, social, and daily functioning, while delaying or ameliorating motor complications of treatment, providing psychological support, and, where possible, preventing psychiatric complications including depression.

Ubiquitin family proteins and their relationship to the proteasome: a structural perspective

Many biological processes rely on targeted protein degradation, the dysregulation of which contributes to the pathogenesis of various diseases. Ubiquitin plays a well-established role in this process, in which the covalent attachment of polyubiquitin chains to protein substrates culminates in their degradation via the proteasome. The three-dimensional structural topology of ubiquitin is highly conserved as a domain found in a variety of proteins of diverse biological function. Some of these so-called "ubiquitin family proteins" have recently been shown to bind components of the 26S proteasome via their ubiquitin-like domains, thus implicating proteasome activity in pathways other than protein degradation. In this chapter, we provide a structural perspective of how the ubiquitin family of proteins interacts with the proteasome.